Let's talk Great Filter

TL;DR – with potentially a billion year headstart on evolution, where the hell are all the :alien:s?

The Fermi paradox or Fermi’s paradox, named after Enrico Fermi, is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations, such as in the Drake equation, and the lack of evidence for such civilizations. The basic points of the argument, made by physicists Enrico Fermi (1901–1954) and Michael H. Hart (born 1932), are:

  • There are billions of stars in the galaxy that are similar to the Sun including many billions of years older than Earth.

  • With high probability, some of these stars will have Earth-like planets, and if the Earth is typical, some might develop intelligent life.

  • Some of these civilizations might develop interstellar travel, a step the Earth is investigating now.

  • Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in about a million years.

According to this line of thinking, the Earth should have already been visited by extraterrestrial aliens. In an informal conversation, Fermi noted no convincing evidence of this, nor any signs of alien intelligence anywhere in the observable universe, leading him to ask, “Where is everybody?”

This is a damn compelling argument, in the same way that the lack of evidence of any time travellers is clear evidence that time travel is not possible… given an infinite amount of time ahead of us.

So what happened – The Great Filter maybe?

With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with “advanced explosive lasting life” must be unlikely. This implies that at least one step in this process must be improbable. Hanson’s list, while incomplete, describes the following nine steps in an “evolutionary path” that results in the colonization of the observable universe:

  • The right star system (including organics and potentially habitable planets)
  • Reproductive molecules (e.g., RNA)
  • Simple (prokaryotic) single-cell life
  • Complex (eukaryotic) single-cell life
  • Sexual reproduction
  • Multi-cell life
  • Tool-using animals with big brains
  • Where we are now
  • Colonization explosion.

According to the Great Filter hypothesis, at least one of these steps must be improbable.

I liked Wait But Why’s take on this a lot, which covers three possibilities:

1) We Are rare

2) We Are :one:st

3) We Are Fucked

So what say you: why are we so alone in the (observable) universe? I grant you that what we can observe is appallingly tiny given the unimaginable scale of the universe, so “what we can observe” may just not be enough by many orders of magnitude.

I have my own ideas, but I’d like to hear what other mutants think.


Obligatory video

Part I was covered on BB previously.


This theory sounds plausible:
[same theory different links and summerizations of it.]

But honestly it’s a little pessimistic for me, I personally like to think of things within the realm of astrophysics, fringe science, quantum mechanics, and the universe at large in a optimistic light and save my pessimism for close to home: humans and earth.


It occurs to me that the 3rd scenario is the only one in which we are unexceptional. Therefore I think it’s the likeliest.


At what sort of distance does all the radio pouring off the Earth become attenuated to fuck-all?

I imagine the inverse square law might be part of the reason we’re not watching alien telly.


Does every topic have to be about fuckin’ Trump? Can we let it go?

Also @kimmo here’s a cool page about radio broadcast distances http://lightyear.fm/


You kind of buried the lede there, though:

“The mystery of why we haven’t yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces”

Sounds plausible, e.g. another significant Great Filter event is that life itself forced planetary climate regulation:

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I’m a fan of the “we’re just not ready” theory.
We’re unsophisticated, hopelessly backwards yokels, rubes on an evolutionary dead end who are hopelessly looking for “sophisticated” life like us, unaware we’re basically algae to other lifeforms.
More charitable is the possibility that a sort of star trek prime directive scenario is playing out.
No, I’m not really serious, still, the idea that we will be able to find signs of intelligent life by looking for something that acts like us is a categorical error we’ve made before.


I think 3) We are fucked. Not because it was inevitable, or because we’re not intelligent, just because we’re so selfish and short-sighted. This doesn’t necessarily say anything about the possibility of intelligent life on other planets, but we just aren’t that good at living sustainably. We think we are or that we’re nearly at that point, which makes it worse. Intelligent beings on other planets who reached or exceeded our technological level may well have gone down the same route of cheating the things that would have controlled their population and ability to consume, so they probably didn’t stand much of a chance long term either.


[quote=“tachin1, post:10, topic:74181”]
hopelessly looking for “sophisticated” life like us, unaware we’re basically algae to other lifeforms.
[/quote] The possibility of evolution of awareness/consciousness/sentience has always intrigued me but whenever I try to look into the actual science around it I always end up neck deep in third eye bullshit. However I totally agree with you in terms of us “just not being ready”, I think it’s similar to the hypothetical levels of civilization (The Kardashev Scale) but for sentience, as a species we are just not yet in possession of the necessary comprehension or sentience to see how flexible “life”, “intellegence”, and the universe can be.


A couple possibilities:

  1. As Kim Stanley Robinson speculated in Aurora, if life evolved on another world, it would likely be so different as to be toxic to anything from ours. Any given life form is inexorably intertwined with the ecosystem from which it came.

  2. We don’t see anything because we are literally being prevented from seeing anything. We are for one reason or another quarantined by the rest of the galactic community. Perhaps it’s a Prime Directive scenario. Maybe we’re a nature preserve. Maybe they’ve observed how violent and territorial we are, and don’t want us to spread. Maybe they’re responsible for panspermia that started life here, and aren’t finished with their experiment.

  3. We are unique among intelligent species. Perhaps other races simply aren’t as curious as us, and have no desire to expand off their homeworld. Maybe they breed at far slower rates or have cognitive functions that take hours or days to do what takes us a split second- Both would severely retard their rate of development. Maybe they are more risk-averse, and would never take on the risks of space travel. It’s been speculated (a few times), that we are actually the most badassed, dangerous predator out there. Maybe they have religious or cultural taboos against technology or space travel. What if they’re just really, really small, and live on a really large planet- It could take them eons to colonize their available land mass before they ever even think about looking up. For whatever reason, aliens just don’t take that step into space.

  4. They are SO alien, we couldn’t even recognize them. We’re going on a very anthropocentric model- Assuming life requires liquid water, that it will be carbon or maybe silicon based, that it will have what we recognize as technology- What if it evolves inside a gas giant, or a SUN? What if their technology is all biological? What if instead of electricity, they use light or x-rays or gamma radiation? What if their species existed as a liquid or gas instead of a solid?


Moss piglets, water bears, Tardigrade; proof that intelligence and enginuity means nothing when you can breed in deep space.


Huge point, and I wish more people were aware of this.

Here is the comprehensible radius of our (and presumably every other civilization that hits that stage) radio broadcasts.

Not the square, the tiny blue dot. That’s it.

I really, REALLY wish people would stop being so freaking Emo about this.

The universe could be absolutely full of civilizations far beyond ours and unless aliens decide to do something that we never have (we made up megastructures as a thought experiment) then we’d never be the wiser.

This comes up so much on a couple of other sites I frequent that I even put together an article hitting on a number of other reasons why Enrico Fermi is probably horrified at how silly we’re being in his name, especially since it’s basically self-traumatization in most cases.

The Tale of Enrico Fermi and the Paradox that Never Was.

Seriously guys. The universe is almost definitely awesome, it’s just not adhering to fantasies we made up when we thought traveling to another planet would be just like getting on a boat. The thought process behind Fermi’s Paradox is closer to Creationism than Science.

The default really shouldn’t be ‘OMGZ everybody diez’, right?


I love this video because it is talking about simulation reality theory to COD bros.

BTW this video is fairly tame on xbox live speak (for those that are sensitive to slurs, cursing, and general douchebaggery). The rest of his videos not so much (I just checked, and basically had to stop watching).

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So are we NPCs or do we go to an existence more boring than this one when we die? (If it were more interesting, why would we even be here?) Or do we just respawn?


I would assume its more like a really in depth version of The Sims. Techinally it doesn’t even have to be a game, just a simulation of life with no real end goal.


If it’s a sim then we’re all just bits of code. It’s not a single player game so much as a game of Sim-Universe. :slightly_smiling:

And, of course, if somebody could make such a simulation (down to the quantum level…those are obviously code artifacts) then statistically there’s a 50% chance you’re there.

Also, of course, if one geek can make a simulation then lots could. So it quickly approaches 100%

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One more possibility is that alien life is so different than the life we are currently familiar with that we don’t even know what we should be looking for.

Example: Let’s say that in a nearby solar system there was an intelligent crystalline life form inhabiting the outer asteroid belt. It’s not just fundamentally different from us biologically, but it exists on an entirely different time scale in which a single thought can take thousands of our years. Would we have the technology to observe such a species? Would we be looking for it even if we did? Would it have the means, motive or interest in contacting us? Would each species even recognize the other for what they were if we did come into contact?


I consider that an ‘in addition’ possibility, along with entities that exist as gaps in potential in clays or brushing up against the accretion disks of black holes.

The thing is, life as we DO know it is pretty much undetectable by any means we have available to us as well if we’re more than a few light years away.

What Fermi’s Paradox is about is life we invented for our Science Fiction books. It’s kind of like how we still haven’t found any cheese moons. :slight_smile: